The process of producing ZnO: Al (AZO) thin films by magnetron sputtering coating
At present, the main thin-film solar cells include: CD (CdTe) thin-film solar cells, se (CIS) thin-film solar cells, amorphous silicon thin-film solar cells and crystalline silicon thin-film solar cells. The researchers have developed a suede ZnO: Al notch structure which is inexpensive, rich in raw materials, non-toxic and stable in performance. AZO transparent conductive film with crater-like suede structure can enhance the scattering effect of sunlight, improve the trapping effect, increase the solar energy absorption of the battery, and improve the conversion efficiency of thin film solar cells. The magnetron sputtering coating process for making AZO transparent conductive film on glass substrate has the advantages of rapid film formation, uniform film layer and large film forming area.
Basic principle of magnetron sputtering coating process: specially designed anode and cathode are placed in the closed vacuum chamber, where the cathode is equipped with spatter material, and Ar, O2, N2 and other process gases are filled in the vacuum chamber. Under the action of external voltage, the process gas molecules produce ionization and form plasma. The positively charged ions are driven to the cathode by the electric field, and they bombard the surface of the target material. The bombarded target atoms deposit at a certain speed to form a thin film on the surface of the glass. In terms of the selection of target materials, there are two types of target materials currently used in the production of transparent conductive film AZO by magnetron sputtering process. A zinc - aluminium alloy target. According to the actual situation, select suitable target products. In terms of the heating temperature of glass substrate, it is shown that the temperature of glass substrate is low, the motion ability of film atoms on the substrate is poor, the film forming speed is reduced, the roughness of film layer is increased, the bonding force between film and glass substrate is weakened, and the resistivity is increased. High glass temperature, be helpful for thin film growth, membrane layer smooth uniform, membrane layer of the sun high light transmittance, general substrate temperature between 200 ~ 300 ℃. In terms of the selection of sputtering gas pressure, the appropriate pressure range of magnetron sputtering is 1.33 x 10-1 Pa ~ 1.33 x 10-2 Pa order of magnitude. If the pressure is too high or too low, it is not conducive to the formation of a good quality AZO transparent conductive film.
As a new TCO material, AZO has great advantages over ITO and FTO. In order to achieve large-scale industrialization, further research and development on how to reduce equipment and process costs must be carried out. Fundamentally, the structural performance of AZO thin films determines their photoelectric performance. More research must be done on the process parameters to achieve a win-win situation of high quality and low cost.
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